#include  <iostream>

template <typename T>
concept int_ = std::is_integral_v<T>;



template<typename T>
concept satistfied = int_<T> && std::is_signed_v<T>;
// https://zhuanlan.zhihu.com/p/266086040
// C11 方式实现concept   enable_if <cond, type> The type T is enabled as member type enable_if::type if Cond is true.

//Otherwise, enable_if::type is not defined.   这里的=0不明白
template <typename T, std::enable_if_t<std::is_integral_v<T>, T> = 0                  >
T add_original(T a, T b) {
	return a + b;
}


template <typename satisfied>
void fun(){



}
